Thermal fatigue of ion implanted magnesium oxide crystals

The present work deals with developing a novel technique suitable for therm al fatigue testing of implanted materials and investigating the cycling fat igue properties of implanted magnesium oxide crystals. Single crystals of M gO were implanted with Si- 90 keV ions with a dose of 5.0 x 10(16) cm(-2) a nd then subjected to thermal cycling in a discharge plasma. The peak cycle temperature and thermal flux were measured using a calorimetric method. The number of thermal cycles prior to an appearance of first cracks and fatigu e limit were evaluated for both the implanted and unimplanted regions. The data demonstrate that ion implantation increases the fatigue life and fatig ue limit of MgO crystals. The analysis suggests the implantation-induced la ttice damage retards the dislocation motion and, thus, reduces the plastic strain during thermal cycling that increases the resistance to the developm ent of fatigue cracks. (C) 1999 Elsevier Science B.V. All rights reserved.